4 Using Shared Storage

Oracle recommends locating specific artifacts in shared storage for a high availability environment.

There are benefits to placing artifacts in a common location that multiple hosts or servers share. This common location typically resides in a shared file system, which is mounted on each server with standard operating system protocols such as NFS and CIFS.

About Shared StorageShared storage allows sharing of dynamic state and server configuration. It simplifies administration, configuration, failover, and backup/recovery.

About Shared Storage

In a highly available environment, shared storage is required when you use file based persistent stores (for JMS and JTA logs) and certain Oracle products. Shared storage is optional for product binaries and domain directories.

The following artifacts are typical candidates to place on a shared file system:

Product binaries: All files and directories related to product executables, JAR files, and scripts that install during product installation.

Shared Storage Prerequisites

There are shared storage prerequisites that apply only when you use file-based persistent stores.

Following are the list of shared storage prerequisites:

For proper recovery in the event of a failure, you must store both JMS and JTA transaction logs in a location that is accessible to all nodes that can resume operations after a Managed Server failure. This setup requires a shared storage location that multiple nodes can reference. See Directory Structure and Configurations for the recommended directory structure.

Oracle recommends that you use a shared storage device that is network-attached storage (NAS) or storage area network (SAN).

If you use NFS-mounted systems, issues related to file locking and abrupt node failures have been detected. See Using File Stores on NFS and check with your storage vendor for the main recommended parameters for mount options.

The following example command is based on a NAS device. Note: your options may be different from those in this example; see UNIX/Linux documentation for more on the mount command.

For maximum availability, Oracle recommends a highly available NAS or SAN device for shared storage. Shared storage devices that are not highly available can be a single point of failure. Check with your storage provider for options to achieve this.

For more on saving JMS and JTA information in a file store, see The WebLogic Persistent Store in Administering the WebLogic Server Persistent Store.

Using Shared Storage for Binary (Oracle Home) Directories

Oracle has guidelines for using shared storage for your Oracle home directories.

About the Binary (Oracle Home) DirectoriesWhen you install any Oracle Fusion Middleware product, you install product binaries into an Oracle home (ORACLE_HOME). The binary files are read-only and don't change unless you patch or upgrade the Oracle home to a newer version

About Sharing a Single Oracle HomeYou can configure multiple servers from one Oracle home. The benefit is that you can install the Oracle home in one location on a shared volume and reuse the Oracle home for multiple servers.

About the Binary (Oracle Home) Directories

When you install any Oracle Fusion Middleware product, you install product binaries into an Oracle home (ORACLE_HOME). The binary files are read-only and don't change unless you patch or upgrade the Oracle home to a newer version

In a typical production environment, you save Oracle home files in a separate location from domain configuration files, which you create using the Configuration Wizard.

About Sharing a Single Oracle Home

You can configure multiple servers from one Oracle home. The benefit is that you can install the Oracle home in one location on a shared volume and reuse the Oracle home for multiple servers.

If multiple servers on different hosts share an Oracle home, there are some best practices to keep in mind. For example, because the Oracle inventory directory (oraInventory) is updated only on the host from which the Oracle home was originally installed, Oracle recommends that you perform all subsequent operations on the Oracle home (such as patching and upgrade) from that original host. If that host is unavailable, ensure that the Oracle inventory is updated on another host before you apply patches or upgrades to the Oracle home from the other host.

About Using Redundant Binary (Oracle Home) Directories

You install two identical Oracle homes for your Oracle Fusion Middleware software on two different shared volumes.

You then mount one of the Oracle homes to one set of servers and the other Oracle home to the remaining servers.

Each Oracle home has the same mount point, so the Oracle home always has the same path, regardless of which Oracle home the server is using.

If one Oracle home becomes corrupted or unavailable, only half your servers are affected. For additional protection, Oracle recommends that you disk mirror these volumes. To restore affected servers to full functionality, you can simply remount the surviving Oracle Home.

If separate volumes are not available on shared storage, Oracle recommends simulating separate volumes using different directories within the same volume and mounting these to the same mount location on the host side. Although this doesn't guarantee the protection that multiple volumes provide, it does protect from user deletions and individual file corruption.

Note:

For maximum protection, Oracle recommends that you evenly distribute the members of a cluster across redundant binary Oracle homes. This is particularly important if cluster members are not running on all available servers.

Using Shared Storage for Domain Configuration Files

There are guidelines for using shared storage for the Oracle WebLogic Server domain configuration files that you create when you configure Oracle Fusion Middleware products in an enterprise deployment.

When you configure an Oracle Fusion Middleware product, you create or extend an Oracle WebLogic Server domain. Each domain consists of a single Administration Server and one or more Managed Servers.

WebLogic uses a replication protocol to push persisted changes on the Administration Server to all Managed Servers. This gives redundancy to the Managed Servers so that you can start them without the Administration Server running. This mode is called Managed Server independence.

Oracle does not require you to store domain configuration files in shared storage. However, to support Administration Server recovery, you must place the Administration Server configuration directory on shared storage and mount it on the host that the Administration Server runs on.